Revolutionary imaging of black hole aims to prove they are not ‘evil vacuum cleaners’ | Black holes
Dark, hungry and inescapable: black holes are often presented as the ultimate cosmic villains.
But now astronomers are preparing to capture film of a supermassive black hole in action for the first time, in observations that could help reveal another side of these elusive – and perhaps misunderstood – space objects.
The Event Horizon Telescope (EHT) will track the colossal black hole at the heart of the Messier 87 galaxy throughout March and April with the goal of capturing images of the swirling disk that traces the edge of the event horizon, the point beyond which no light or matter can escape.
“The film campaign is truly revolutionary, not only because it is extremely technologically demanding, but also because it will accelerate our science by an order of magnitude,” said Sera Markoff, the new Plumian Professor of Astronomy and Experimental Philosophy at the University of Cambridge and a founding member of the EHT consortium.
“We may be able to better understand the black hole’s rotation speed and how black holes launch jets, two major outstanding questions in our field.”
Black holes, she added, have a reputation for being “scary” objects, but are increasingly recognized by scientists as holding the key to understanding how the first galaxies appeared in the early universe and their subsequent evolution.
“Black holes have a bad reputation as evil vacuum cleaners that suck up everything,” she said. “To me, they represent the limit of our understanding of our universe and they are endlessly fascinating. They actually play a very important role in the ecosystem of the universe.
The EHT is a global network of 12 radio telescopes stretching from Antarctica to Spain and Korea, which in 2019 revealed the first image of the shadow of a black hole. In March and April, as the Earth rotates, M87’s central black hole will be visible to different telescopes, allowing a full image to be captured every three days.
The scale of the black hole – its mass is the equivalent of 6 billion suns and its surface area is the size of the solar system – means it is moving slowly enough for these snapshots to be stitched together into an animated sequence.
Measuring the black hole’s rotation speed is important because it could help distinguish between competing theories about how these objects reached such epic proportions. If black holes grow primarily through accretion – that is, a constant snowball moving away from nearby locations – we would expect them to eventually spin at incredibly high speeds. On the other hand, if black holes grow primarily through mergers with other black holes, each merger could slow things down.
The observations could also help explain how black hole jets, which are among the largest and most powerful structures produced by galaxies, form. The jets channel vast columns of gas out of galaxies, slowing the formation of new stars and limiting galaxy growth. In turn, this can create dense pockets of material that trigger bursts of star formation beyond the host galaxy.
“M87 launches these huge jets that go across the entire galaxy,” Markoff said. “They can change the entire evolution of the galaxy and even surrounding galaxies.”
Although the film campaign will take place in the spring, the sheer volume of data produced by the telescopes means that scientists will have to wait until the Antarctic summer before they can physically ship the hard drives to Germany and the United States for processing. So it will likely be a long time before the rest of the world gets a glimpse of the black hole in action.
Markoff was announced in December as the 17th Plumian Professor, one of the oldest named professorships in the world. Sir Isaac Newton oversaw the creation of the post in 1704, with former Plumians including the eminent astronomers Sir Arthur Eddington, Sir Fred Hoyle and Lord Martin Rees. Markoff says she hopes to use this position to encourage more people from underrepresented backgrounds to go into science.
“I don’t come from a scientific or academic family, so my interest in astrophysics came simply from reading science fiction and comic books,” she said. “Given that I was thinking about going to art school, it was a pretty strange thing for me to be interested in, but those books exposed me to the ideas of black holes and instilled in me a desire to explore the universe. I was also fortunate to have many supportive teachers, but I never seriously thought I could pursue a career like this. Now I like to joke that I do science fiction to earn my life.”
